1. Field of the Invention
The present invention relates to a display device in which a display screen of a display panel mounted in a case main body is covered with a transparent cover, and more particularly to a display device in which anti-dust and anti-fog measures are taken for preventing dust and the like from entering a space defined between the display panel and the cover and for preventing occurrence of fogging due to condensation.
2. Description of the Related Art
In a display device that is to be mounted in a vehicle and that is to be arranged in a cluster panel or the like provided in a vehicle cabin, a display unit is mounted on the backside of a case main body having an opening, and a display panel (a liquid crystal panel) that is a component member of the display unit is exposed through the opening of the case main body. However, the opening of the case main body is usually covered with a transparent cover in such a manner as to prevent a display screen of the display panel from getting damaged. In this case, if a large space is not secured between the cover and the display screen, when the cover is pressed by a finger of an occupant or the like and is warped, the deformation of the cover may directly affect the display panel, and the display screen can be damaged. Thus, a reasonably large space is secured between the cover and the display screen.
In such a display device to be mounted in a vehicle, in the case where the space is not hermetically sealed and is in an open state, foreign objects such as dust are likely to enter the space from the outside. In contrast, in a state where the space is completely hermetically sealed, water vapor that is present in the space is likely to condense on the cover and the display screen in a low temperature environment, and thus, a problem occurs in that the display screen becomes fogged and difficult to see. Therefore, in the related art, there has been proposed a display device, which is to be mounted in a vehicle, in which a plurality of air holes are formed in an outer circumferential portion of a cover, a frame-shaped dustproof sheet that is breathable is attached to the outer circumferential portion of the cover in such a manner as to cover the air holes, and a display unit is mounted on the backside of a case main body in such a manner that a multilayer body formed of the cover and the dustproof sheet is sandwiched between the display unit and the case main body, so that the air holes of the cover overlapping with the space are in communication with an external space via recesses of the case main body (see Japanese Unexamined Patent Application Publication No. 2011-133783). In this example of the related art, the space defined between the cover and the display unit is surrounded by the frame-shaped dustproof sheet, and thus, the dustproof sheet can prevent dust and the like from entering the space. In addition, since the air holes of the cover are in communication with the external space via the recesses of the case main body, condensation is not likely to occur in the space, and thus, a good anti-fogging effect can be expected.
However, in the display device to be mounted in a vehicle of the related art disclosed in Japanese Unexamined Patent Application Publication No. 2011-133783, the dustproof sheet needs to be formed by punching a piece of nonwoven fabric or the like into a frame-like shape, and after that, the dustproof sheet needs to be attached to the outer circumferential portion of the cover using a double-sided adhesive tape or the like. Thus, the component costs including the costs of the dustproof sheet and the double-sided adhesive tape significantly increase, and as a result, there has been a problem in that the efficiency of assembly work of attaching the dustproof sheet to the cover is poor. In addition, since the display unit is mounted on the backside of the case main body in such a manner that the display unit is pressed into contact with the rear surface of the dustproof sheet, so that the space is secured between the rear surface of the cover and the display screen of the display panel, the depth dimension of the space cannot be set sufficiently large, and there is a possibility that the display screen gets damaged due to the deflection deformation of the cover.